编译原理(五) LL(1)文法分析法(预测分析表的构造算法C++实现)

基本定义

• FIRST(α):
  
  • 令Ｇ是一个不含左递归的文法，对G的所有非终结符的每个候选α定义它的终结首符集FIRST(α)为：
    FIRST(α)={a | α=>*a…, a∈VT}
  • 若α=>*ε，则规定ε∈FIRST(α)
  • FIRST(α)是α的所有可能推导的开头终结符或可能的ε
  • 如果非终结符Ａ的所有候选首符集两两不相交，即Ａ的任何两个不同候选αi和αｊ
    FIRST(αi) ∩FIRST(αj)=Φ
  • 那么当要求Ａ匹配输入串时，Ａ就能根据它所面临的第一个输入符号ａ，准确的指派某一个候选前去执行任务。这个候选就是那个终结首符集含ａ的α。
• FOLLOW(A) :
  
  • 假定S是文法G的开始符号，对于G的任何非终结符A，我们定义
    FOLLOW(A)={a | S=>*…Aa…，a∈VT}
  • FOLLOW(A)是所有句型中出现在紧接A之后的终结符或“#”。开始符号的FOLLOW集初始化时加入“#”。
  • 当非终结符A面临输入符号a，且a不属于A的任意候选首符集但A的某个候选首符集包含ε时，只有当a∈FOLLOW(A)时，才可能允许A自动匹配。
• LL(1)文法 :
  
  • 文法不含左递归
  • 对于文法中每一个非终结符A的各个产生式的候选首符集两两不相交。即，若A→α1 |α2 | … |αn，则FIRST(αi)∩FIRST(αj)=Φ (i≠j)
  • 对文法中的每个非终结符A，若它存在某个候选首符集包含ε，则，FIRST(A)∩FOLLOW(A)=Φ
    如果一个文法G满足以上条件，则称该文法G为LL(1)文法。
  • LL(1)文法是不带回溯的自顶向下的文法
• 预测分析表：
  
  • 预测分析表示一个M[A,a]形式的矩阵。其中A为非终结符，a是终结符或‘#’ 。
  • 矩阵元素M[A,a]中存放着一条关于A的产生式，指出当A面临输入符号a时所应采用的候选。
    M[A,a]中也可能存放一个“出错标志”，指出A根本不该面临输入符号a。

预测分析表的构造

FIRST(α)的构造算法

要构造 FIRST(α) ，根据定义：
α=X1⋯Xn
那么对于从前到后的 Xi 我们进行分类讨论：

• 如果 Xi∈Vt,那么FIRST(α)=FIRST(Xi)={Xi}
• 如果 Xi∈Vn,因为不存在左递归，所以Xi=a.......|ϵ,那么FIRST(Xi)={a,ϵ,FIRST(Xi+1)}
• 只要 Xi−1不包含ϵ,那么Xi不可能影响FIRST(α)
• 那么我们通过记录每个 a∈V ,然后进行深度优先记忆化搜索,将所有的状态填满，因为LL(1)文法使不会回溯的，所以能够保证在 O(n)的时间完成 ，采取递归的形式实现

FIRST(α)的构造实现代码

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#define MAX 507

using namespace std;


//大写字母为非终止符(可以多一个'的标号做区分)，小写字母为终止符,用~代替epsilon
class WF
{
    public:
    string left;
    set<string> right;
    WF ( char s[] )
    {
        left = s;
    }
    void print ( )
    {
        printf ( "%s->" , left.c_str() );
        set<string>::iterator it = right.begin();
        if ( right.begin()!= right.end() )
        {
            printf ( "%s" , it->c_str() );
            it++;
        }
        for(; it != right.end() ; it++ )
            printf ( "|%s" , it->c_str() );
        puts("");
    }
    void insert ( char s[] )
    {
        right.insert ( s );
    }
};

map<string,set<char> > first;
map<string,set<char> > follow;
map<string,int> VN_dic;
vector VN_set;
bool used[MAX];

void dfs ( int x )
{
    if ( used[x] ) return;
    used[x] = 1;
    string& left = VN_set[x].left;
    set<string>& right = VN_set[x].right;
    set<string>::iterator it = right.begin();
    for ( ; it!= right.end() ; it++ )
        for ( int i = 0 ; i < it->length() ; i++ )
        {
            if ( !isupper( it->at(i) ) && it->at(i) != '\'' )
            {
                first[left].insert ( it->at(i) );
                break;
            }
            if ( isupper( it->at(i) ) )
            {
                int y;
                if ( i != it->length()-1 && it->at(i+1) == '\'' )
                    y = VN_dic[it->substr(i,2)]-1;
                else y = VN_dic[it->substr(i,1)]-1;
                string& tleft = VN_set[y].left;
                dfs ( y );
                set<char>& temp = first[tleft];
                set<char>::iterator it1 = temp.begin();
                bool flag = true;
                for ( ; it1 != temp.end() ; it1++ )
                {
                    if ( *it1 == '~' ) flag = false;
                    first[left].insert( *it1 );
                }
                if ( flag ) break;
            }
            else continue;
        }
}

void make_first ( )
{
    memset ( used , 0 , sizeof ( used ) );
    for ( int i = 0 ; i < VN_set.size() ; i++ )
        dfs ( i );
#define DEBUG
#ifdef DEBUG
        map<string,set<char> >::iterator it = first.begin();
        for ( ; it != first.end() ; it++ )
        {
            printf ( "FIRST(%s)={" , it->first.c_str() );
            set<char> & temp = it->second;
            set<char>::iterator it1 = temp.begin();
            bool flag = false;
            for ( ; it1 != temp.end() ; it1++ )
            {
                if ( flag ) printf ( "," );
                printf ( "%c" , *it1 );
                flag = true;
            }
            puts ("}");
        }
#endif
}

int main ( )
{
    int n;
    char s[MAX];
    while ( ~scanf ( "%d" , &n ) )
    {
        for ( int i = 0 ; i < n ; i++ )
        {
            scanf ( "%s" , s );
            int len = strlen ( s ),j;
            for ( j = 0 ; j < len ; j++ )
                if ( s[j] == '-' ) break;
            s[j] = 0;
            if ( !VN_dic[s] )
            {
                VN_set.push_back ( s );
                VN_dic[s] = VN_set.size();
            }
            int x = VN_dic[s]-1;
            VN_set[x].insert ( s+j+2 );
        }
        make_first();
    }
}

Input:

Output:

FOLLOW(A)的构造算法

设S,A,B∈Vn,那么连续使用如下规则，直至follow集不再发生变化：

• （1） S为标识符，那么FOLLOW(S)包含“#”
• （2） 若 A::=αBβ,那么FOLLOW(B)+=FIRST(B)−{ϵ}
• （3） 若 A::=αB或者A::=αBβ,且β⇒∗ϵ，那么FOLLOW(B)+=FOLLOW(A)

FOLLOW(A)的构造实现代码

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#define MAX 507

using namespace std;


//大写字母为非终止符(可以多一个'的标号做区分)，小写字母为终止符,用~代替epsilon
class WF
{
    public:
    string left;
    set<string> right;
    WF ( char s[] )
    {
        left = s;
    }
    void print ( )
    {
        printf ( "%s->" , left.c_str() );
        set<string>::iterator it = right.begin();
        if ( right.begin()!= right.end() )
        {
            printf ( "%s" , it->c_str() );
            it++;
        }
        for(; it != right.end() ; it++ )
            printf ( "|%s" , it->c_str() );
        puts("");
    }
    void insert ( char s[] )
    {
        right.insert ( s );
    }
};

map<string,set<char> > first;
map<string,set<char> > follow;
map<string,int> VN_dic;
vector VN_set;
bool used[MAX];

void dfs ( int x )
{
    if ( used[x] ) return;
    used[x] = 1;
    string& left = VN_set[x].left;
    set<string>& right = VN_set[x].right;
    set<string>::iterator it = right.begin();
    for ( ; it!= right.end() ; it++ )
        for ( int i = 0 ; i < it->length() ; i++ )
        {
            if ( !isupper( it->at(i) ) && it->at(i) != '\'' )
            {
                first[left].insert ( it->at(i) );
                break;
            }
            if ( isupper( it->at(i) ) )
            {
                int y;
                if ( i != it->length()-1 && it->at(i+1) == '\'' )
                    y = VN_dic[it->substr(i,2)]-1;
                else y = VN_dic[it->substr(i,1)]-1;
                string& tleft = VN_set[y].left;
                dfs ( y );
                set<char>& temp = first[tleft];
                set<char>::iterator it1 = temp.begin();
                bool flag = true;
                for ( ; it1 != temp.end() ; it1++ )
                {
                    if ( *it1 == '~' ) flag = false;
                    first[left].insert( *it1 );
                }
                if ( flag ) break;
            }
            else continue;
        }
}

void make_first ( )
{
    memset ( used , 0 , sizeof ( used ) );
    for ( int i = 0 ; i < VN_set.size() ; i++ )
        dfs ( i );
#define DEBUG
#ifdef DEBUG
        puts ("***************FIRST集***********************");
        map<string,set<char> >::iterator it = first.begin();
        for ( ; it != first.end() ; it++ )
        {
            printf ( "FIRST(%s)={" , it->first.c_str() );
            set<char> & temp = it->second;
            set<char>::iterator it1 = temp.begin();
            bool flag = false;
            for ( ; it1 != temp.end() ; it1++ )
            {
                if ( flag ) printf ( "," );
                printf ( "%c" , *it1 );
                flag = true;
            }
            puts ("}");
        }
#endif
}

void append ( const string& str1 , const string& str2 )
{
    set<char>& from = follow[str1];
    set<char>& to = follow[str2];
    set<char>::iterator it = from.begin();
    for ( ; it != from.end() ; it++ )
        to.insert ( *it );
}

void make_follow ( )
{
    while ( true )
    {
        bool goon = false;
        for ( int i = 0 ; i < VN_set.size() ; i++ )
        {
            string& left = VN_set[i].left;
            set<string>& right = VN_set[i].right;
            set<string>::iterator it = right.begin();
            for ( ; it!= right.end() ; it++ )
            {
                bool flag = true;
                const string& str = *it;
                for ( int j = it->length()-1 ; j >= 0 ; j-- )
                {
                    if ( str[j] == '\'' )
                    {
                        int x = VN_dic[it->substr(j-1,2)]-1;
                        if ( flag ) 
                        {
                            int tt = follow[it->substr(j-1,2)].size();
                            append ( left , it->substr(j-1,2) );
                            int tt1 = follow[it->substr(j-1,2)].size();
                            if ( tt1 > tt ) goon = true;
                            if ( !VN_set[x].right.count("~" ) ) 
                                flag = false;
                        }
                        for ( int k = j+1 ; k < it->length() ; k++ )
                        {
                            if ( isupper(str[k]) )
                            {
                                string id;
                                if ( k != it->length()-1 && str[k+1] == '\'' )
                                    id = it->substr(k,2);
                                else id = it->substr(k,1);
                                set<char>& from = first[id];
                                set<char>& to = follow[it->substr(j-1,2)];
                                int tt = to.size();
                                set<char>::iterator it1 = from.begin();
                                for ( ; it1 != from.end() ; it1++ )
                                    if ( *it1 != '~' )
                                        to.insert ( *it1 );
                                int tt1 = follow[it->substr(j-1,2)].size();
                                if ( tt1 > tt ) goon = true;
                                if ( !VN_set[VN_dic[id]-1].right.count("~") )
                                    break;
                            }
                            else if ( str[k] != '\'' )
                            {
                                int tt = follow[it->substr(j-1,2)].size();
                                follow[it->substr(j-1,2)].insert ( str[k] );
                                int tt1 = follow[it->substr(j-1,2)].size();
                                if ( tt1 > tt )
                                    goon = true;
                                break;
                            }
                            else continue;
                        }
                        j--;
                    }
                    else if ( isupper(str[j] ) )
                    {
                        int x = VN_dic[it->substr(j,1)]-1;
                        if ( flag )
                        {
                            int tt = follow[it->substr(j,1)].size();
                            append ( left , it->substr(j,1) );
                            if ( !VN_set[x].right.count("~") )
                                flag = false;
                            int tt1 = follow[it->substr(j,1)].size();
                            if ( tt1 > tt ) goon = true;
                        }
                        for ( int k = j+1 ; k < it->length() ; k++ )
                        {
                            if ( isupper( str[k] ) )
                            {
                                string id;
                                if ( k != it->length()-1 && str[k+1] == '\'' )
                                    id = it->substr(k,2);
                                else id = it->substr(k,1);
                                set<char>& from = first[id];
                                set<char>& to = follow[it->substr(j,1)];
                                set<char>::iterator it1 = from.begin();
                                int tt = follow[it->substr(j,1)].size();
                                for ( ; it1 != from.end() ; it1++ )
                                    if ( *it1 != '~' )
                                        to.insert( *it1 );
                                int tt1 = follow[it->substr(j,1)].size();
                                if ( tt1 > tt ) goon = true;
                                if ( !VN_set[VN_dic[id]-1].right.count("~") )
                                    break;
                            }
                            else if ( str[k] != '\'' )
                            {
                                int tt = follow[it->substr(j,1)].size();
                                follow[it->substr(j,1)].insert ( str[k] );
                                int tt1 = follow[it->substr(j,1)].size();
                                if ( tt1 > tt ) goon = true;
                                break;
                            }
                            else continue;
                        }
                    }
                    else flag = false;
                }
            }
        }
        if ( !goon ) break;
    }
#define DEBUG
#ifdef DEBUG
    puts ("****************FOLLOW集**********************" );
    map<string,set<char> >::iterator it = follow.begin();
    for ( ; it != follow.end() ; it++ )
    {
        printf ( "FOLLOW(%s)={" , it->first.c_str() );
        set<char> & temp = it->second;
        temp.insert('#');
        set<char>::iterator it1 = temp.begin();
        bool flag = false;
        for ( ; it1 != temp.end() ; it1++ )
        {
            if ( flag ) printf ( "," );
            printf ( "%c" , *it1 );
            flag = true;
        }
        puts ("}");
    }
#endif
}

int main ( )
{
    int n;
    char s[MAX];
    while ( ~scanf ( "%d" , &n ) )
    {
        for ( int i = 0 ; i < n ; i++ )
        {
            scanf ( "%s" , s );
            int len = strlen ( s ),j;
            for ( j = 0 ; j < len ; j++ )
                if ( s[j] == '-' ) break;
            s[j] = 0;
            if ( !VN_dic[s] )
            {
                VN_set.push_back ( s );
                VN_dic[s] = VN_set.size();
            }
            int x = VN_dic[s]-1;
            VN_set[x].insert ( s+j+2 );
        }
        make_first();
        make_follow();
    }
}

Input:

Output:

预测分析表的构造算法

预测分析表的构造实现代码

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#define MAX 507

using namespace std;


//大写字母为非终止符(可以多一个'的标号做区分)，小写字母为终止符,用~代替epsilon
class WF
{
    public:
    string left;
    set<string> right;
    WF ( char s[] )
    {
        left = s;
    }
    void print ( )
    {
        printf ( "%s->" , left.c_str() );
        set<string>::iterator it = right.begin();
        if ( right.begin()!= right.end() )
        {
            printf ( "%s" , it->c_str() );
            it++;
        }
        for(; it != right.end() ; it++ )
            printf ( "|%s" , it->c_str() );
        puts("");
    }
    void insert ( char s[] )
    {
        right.insert ( s );
    }
};

map<string,set<char> > first;
map<string,set<char> > follow;
map<string,int> VN_dic;
vector VN_set;
bool used[MAX];

void dfs ( int x )
{
    if ( used[x] ) return;
    used[x] = 1;
    string& left = VN_set[x].left;
    set<string>& right = VN_set[x].right;
    set<string>::iterator it = right.begin();
    for ( ; it!= right.end() ; it++ )
        for ( int i = 0 ; i < it->length() ; i++ )
        {
            if ( !isupper( it->at(i) ) && it->at(i) != '\'' )
            {
                first[left].insert ( it->at(i) );
                break;
            }
            if ( isupper( it->at(i) ) )
            {
                int y;
                if ( i != it->length()-1 && it->at(i+1) == '\'' )
                    y = VN_dic[it->substr(i,2)]-1;
                else y = VN_dic[it->substr(i,1)]-1;
                string& tleft = VN_set[y].left;
                dfs ( y );
                set<char>& temp = first[tleft];
                set<char>::iterator it1 = temp.begin();
                bool flag = true;
                for ( ; it1 != temp.end() ; it1++ )
                {
                    if ( *it1 == '~' ) flag = false;
                    first[left].insert( *it1 );
                }
                if ( flag ) break;
            }
            else continue;
        }
}

void make_first ( )
{
    memset ( used , 0 , sizeof ( used ) );
    for ( int i = 0 ; i < VN_set.size() ; i++ )
        dfs ( i );
#define DEBUG
#ifdef DEBUG
        puts ("***************FIRST集***********************");
        map<string,set<char> >::iterator it = first.begin();
        for ( ; it != first.end() ; it++ )
        {
            printf ( "FIRST(%s)={" , it->first.c_str() );
            set<char> & temp = it->second;
            set<char>::iterator it1 = temp.begin();
            bool flag = false;
            for ( ; it1 != temp.end() ; it1++ )
            {
                if ( flag ) printf ( "," );
                printf ( "%c" , *it1 );
                flag = true;
            }
            puts ("}");
        }
#endif
}

void append ( const string& str1 , const string& str2 )
{
    set<char>& from = follow[str1];
    set<char>& to = follow[str2];
    set<char>::iterator it = from.begin();
    for ( ; it != from.end() ; it++ )
        to.insert ( *it );
}

void make_follow ( )
{
    while ( true )
    {
        bool goon = false;
        for ( int i = 0 ; i < VN_set.size() ; i++ )
        {
            string& left = VN_set[i].left;
            set<string>& right = VN_set[i].right;
            set<string>::iterator it = right.begin();
            for ( ; it!= right.end() ; it++ )
            {
                bool flag = true;
                const string& str = *it;
                for ( int j = it->length()-1 ; j >= 0 ; j-- )
                {
                    if ( str[j] == '\'' )
                    {
                        int x = VN_dic[it->substr(j-1,2)]-1;
                        if ( flag ) 
                        {
                            int tt = follow[it->substr(j-1,2)].size();
                            append ( left , it->substr(j-1,2) );
                            int tt1 = follow[it->substr(j-1,2)].size();
                            if ( tt1 > tt ) goon = true;
                            if ( !VN_set[x].right.count("~" ) ) 
                                flag = false;
                        }
                        for ( int k = j+1 ; k < it->length() ; k++ )
                        {
                            if ( isupper(str[k]) )
                            {
                                string id;
                                if ( k != it->length()-1 && str[k+1] == '\'' )
                                    id = it->substr(k,2);
                                else id = it->substr(k,1);
                                set<char>& from = first[id];
                                set<char>& to = follow[it->substr(j-1,2)];
                                int tt = to.size();
                                set<char>::iterator it1 = from.begin();
                                for ( ; it1 != from.end() ; it1++ )
                                    if ( *it1 != '~' )
                                        to.insert ( *it1 );
                                int tt1 = follow[it->substr(j-1,2)].size();
                                if ( tt1 > tt ) goon = true;
                                if ( !VN_set[VN_dic[id]-1].right.count("~") )
                                    break;
                            }
                            else if ( str[k] != '\'' )
                            {
                                int tt = follow[it->substr(j-1,2)].size();
                                follow[it->substr(j-1,2)].insert ( str[k] );
                                int tt1 = follow[it->substr(j-1,2)].size();
                                if ( tt1 > tt )
                                    goon = true;
                                break;
                            }
                            else continue;
                        }
                        j--;
                    }
                    else if ( isupper(str[j] ) )
                    {
                        int x = VN_dic[it->substr(j,1)]-1;
                        if ( flag )
                        {
                            int tt = follow[it->substr(j,1)].size();
                            append ( left , it->substr(j,1) );
                            if ( !VN_set[x].right.count("~") )
                                flag = false;
                            int tt1 = follow[it->substr(j,1)].size();
                            if ( tt1 > tt ) goon = true;
                        }
                        for ( int k = j+1 ; k < it->length() ; k++ )
                        {
                            if ( isupper( str[k] ) )
                            {
                                string id;
                                if ( k != it->length()-1 && str[k+1] == '\'' )
                                    id = it->substr(k,2);
                                else id = it->substr(k,1);
                                set<char>& from = first[id];
                                set<char>& to = follow[it->substr(j,1)];
                                set<char>::iterator it1 = from.begin();
                                int tt = follow[it->substr(j,1)].size();
                                for ( ; it1 != from.end() ; it1++ )
                                    if ( *it1 != '~' )
                                        to.insert( *it1 );
                                int tt1 = follow[it->substr(j,1)].size();
                                if ( tt1 > tt ) goon = true;
                                if ( !VN_set[VN_dic[id]-1].right.count("~") )
                                    break;
                            }
                            else if ( str[k] != '\'' )
                            {
                                int tt = follow[it->substr(j,1)].size();
                                follow[it->substr(j,1)].insert ( str[k] );
                                int tt1 = follow[it->substr(j,1)].size();
                                if ( tt1 > tt ) goon = true;
                                break;
                            }
                            else continue;
                        }
                    }
                    else flag = false;
                }
            }
        }
        if ( !goon ) break;
    }
#define DEBUG
#ifdef DEBUG
    puts ("****************FOLLOW集**********************" );
    map<string,set<char> >::iterator it = follow.begin();
    for ( ; it != follow.end() ; it++ )
    {
        printf ( "FOLLOW(%s)={" , it->first.c_str() );
        set<char> & temp = it->second;
        temp.insert('#');
        set<char>::iterator it1 = temp.begin();
        bool flag = false;
        for ( ; it1 != temp.end() ; it1++ )
        {
            if ( flag ) printf ( "," );
            printf ( "%c" , *it1 );
            flag = true;
        }
        puts ("}");
    }
#endif
}

vector<map<char,string> > predict_table;

//检查一个字符是否属于一个字符串的FIRST集合
bool check_first ( const string& text , char ch )
{
    for ( int i = 0 ; i < text.length() ; i++ )
    {
        bool hasEmpty = false;
        if ( !isupper(text[i]) && text[i] != '\'' )
        {
            if ( text[i] != ch ) return false;
            else return true;
        }
        else if ( isupper(text[i] ) )
        {
            string temp;
            if ( i != text.length()-1 && text[i+1] == '\'' )
                temp = text.substr(i,2);
            else
                temp = text.substr(i,1);
            set<char>& dic = first[temp];
            set<char>::iterator it = dic.begin();
            for ( ; it != dic.end() ; it++ )
            {
                if ( *it == '~' ) hasEmpty = true;
                if ( *it == ch ) return true;
            }
            if ( !hasEmpty) break;
        }
        else continue;
    }
    return false;
}

//检查一个字符是否属于一个字符串的FOLLOW集合
bool check_follow ( const string& text , char ch )
{
    set<char>& dic = follow[text];
    set<char>::iterator it = dic.begin();
    for ( ; it != dic.end() ; it++ )
        if ( *it == ch ) return true;
    return false;
}

void make_table ()
{
    map<char,string> temp;
    vector<char> letter;
    bool vis[500];
    memset ( vis , 0 , sizeof ( vis ) );
    for ( int i = 0 ; i < VN_set.size() ; i++ )
    {
        set<string>& right = VN_set[i].right;
        set<string>::iterator it = right.begin();
        for ( ; it != right.end() ; it++ )
            for ( int j = 0 ; j < it->length() ; j++ )
                if ( !isupper(it->at(j)) && it->at(j) != '\'' ) 
                {
                    if ( vis[it->at(j)] ) continue;
                    vis[it->at(j)] = true;
                    letter.push_back ( it->at(j) );
                }
    }
    for ( int i = 0 ; i < VN_set.size() ; i++ )
    {
        temp.clear();
        string& left = VN_set[i].left;
        set<string>& right = VN_set[i].right;
        set<string>::iterator it = right.begin();
        for ( ; it != right.end() ; it++ )
            for ( int j = 0 ; j < letter.size() ; j++ )
            {
                //cout << *it << " " <<  letter[j] << endl;
                if ( check_first ( *it , letter[j] ) )
                {
                    //cout << "YES" << endl;
                    temp[letter[j]] = *it;
                }
                if ( it->at(0) == '~' && check_follow ( left, letter[j] ))
                    temp[letter[j]] = *it;
            }
        predict_table.push_back ( temp );
    }
#define DEBUG
#ifdef DEBUG
    for ( int i = 0 ; i <= (letter.size()+1)*10 ; i++ )
        printf ( "-" );
    puts ("");
    printf ( "|%9s" , "|" );
    for ( int i = 0 ; i < letter.size() ; i++ )
        printf ( "%5c%5s" , letter[i] , "|" );
    puts("");
    for ( int i = 0 ; i <= (letter.size()+1)*10 ; i++ )
        printf ( "-" );
    puts("");
    for ( int i = 0 ; i < VN_set.size() ; i++ )
    {
        printf ( "|%5s%4s" , VN_set[i].left.c_str() , "|" );
        for ( int j = 0 ; j < letter.size() ; j ++ )
            if ( predict_table[i].count(letter[j] ) )
                printf ( "%7s%3s" , predict_table[i][letter[j]].c_str() , "|" );
            else printf ( "%10s" , "|" );
        puts("");
        for ( int i = 0 ; i <= (letter.size()+1)*10 ; i++ )
            printf ( "-" );
        puts ("");
    }
#endif
}

int main ( )
{
    int n;
    char s[MAX];
    while ( ~scanf ( "%d" , &n ) )
    {
        for ( int i = 0 ; i < n ; i++ )
        {
            scanf ( "%s" , s );
            int len = strlen ( s ),j;
            for ( j = 0 ; j < len ; j++ )
                if ( s[j] == '-' ) break;
            s[j] = 0;
            if ( !VN_dic[s] )
            {
                VN_set.push_back ( s );
                VN_dic[s] = VN_set.size();
            }
            int x = VN_dic[s]-1;
            VN_set[x].insert ( s+j+2 );
        }
        make_first();
        make_follow();
        make_table();
    }
}

Input:

Output: